A dietary supplement is intended to provide nutrients that may otherwise not be consumed in sufficient quantities.

Supplements as generally understood include vitamins, minerals, fiber, fatty acids, or amino acids, among other substances. U.S. authorities define dietary supplements as foods, while elsewhere they may be classified as drugs or other products.

There are more than 50,000 dietary supplements available. More than half of the U.S. adult population (53% - 55%) consume dietary supplements with most common ones being multivitamins.[1][2]

These products are not intended to prevent or treat any disease and in some circumstances are dangerous, according to the U.S. National Institutes of Health. For those who fail to consume a balanced diet, the agency says that certain supplements "may have value."[3]

Most supplements should be avoided, and usually people should not eat micronutrients except people with clearly shown deficiency.[4] Those people should first consult a doctor.[5] An exception is vitamin D, which is recommended in Nordic countries[6] due to weak sunlight.

In the United States, the FDA has different monitoring procedures for substances depending on whether they are presented as drugs, food additives, food, or dietary supplements.[7] Dietary supplements are eaten or taken by mouth, and are regulated in United States law as a type of food rather than a type of drug.[8] Like food and unlike drugs, no government approval is required to make or sell dietary supplements; the manufacturer checks the safety of dietary supplements but the government does not; and rather than requiring risk–benefit analysis to prove that the product can be sold like a drug, risk–benefit analysis is only used to petition that food or a dietary supplement is unsafe and should be removed from market.[7]

Medical uses

The intended use of dietary supplements is to ensure that a person gets enough essential nutrients.[9]

Supplements may create harm in several ways, including over-consumption, particularly of minerals and fat-soluble vitamins which can build up in the body.[12] The products may also cause harm related to their rapid absorption in a short period of time, quality issues such as contamination, or by adverse interactions with other foods and medications.[13]

Types of dietary supplements

There are many types of dietary supplements.

Vitamins

Vitamin is an organic compound required by an organism as a vital nutrient in limited amounts.[14] An organic chemical compound (or related set of compounds) is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on the circumstances and on the particular organism. For example, ascorbic acid (vitamin C) is a vitamin for humans, but not for most other animals. Supplementation is important for the treatment of certain health problems but there is little evidence of benefit when used by those who are otherwise healthy.[15]

Herbal medicine

Herbal medicine is the use of plants for medicinal purposes. Plants have been the basis for medical treatments through much of human history, and such traditional medicine is still widely practiced today. Modern medicine recognizes herbalism as a form of alternative medicine, as the practice of herbalism is not strictly based on evidence gathered using the scientific method. Modern medicine, does, however, make use of many plant-derived compounds as the basis for evidence-tested pharmaceutical drugs, and phytotherapy works to apply modern standards of effectiveness testing to herbs and medicines that are derived from natural sources. The scope of herbal medicine is sometimes extended to include fungal and bee products, as well as minerals, shells and certain animal parts.

Amino acids can be divided into three categories: essential amino acids, non-essential amino acids, and conditional amino acids. Essential amino acids cannot be made by the body, and must be supplied by food. Non-essential amino acids are made by the body from essential amino acids or in the normal breakdown of proteins. Conditional amino acids are usually not essential, except in times of illness, stress, or for someone challenged with a lifelong medical condition[citation needed].

Essential fatty acids

Essential fatty acids, or EFAs, are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them.[16] The term "essential fatty acid" refers to fatty acids required for biological processes but does not include the fats that only act as fuel.

Bodybuilding supplements

Bodybuilding supplements are dietary supplements commonly used by those involved in bodybuilding and athletics. Bodybuilding supplements may be used to replace meals, enhance weight gain, promote weight loss or improve athletic performance. Among the most widely used are vitamin supplements, protein drinks, branched-chain amino acids (BCAA), glutamine, essential fatty acids, meal replacement products, creatine, weight loss products and testosterone boosters. Supplements are sold either as single ingredient preparations or in the form of "stacks" - proprietary blends of various supplements marketed as offering synergistic advantages. While many bodybuilding supplements are also consumed by the general public their salience and frequency of use may differ when used specifically by bodybuilders.

Contraindications

According to University of Helsinki food safety professor Marina Heinonen, more than 90% of dietary supplement health claims are incorrect.[17]

Adverse effects

Some products make extraordinary claims and contain active ingredients which may not have been proven effective.

The number of incidents of liver damage from dietary supplements has tripled in a decade. Most of the supplements were bodybuilding supplements. Some of the patients require liver transplants and some die. In third of the supplements involved contained unlisted steroids.[18]

Physical and chemical properties

Adulteration in North America

BMC Medicine published a study on herbal supplements. Most of the supplements studied were of low quality, a third did not contain the herb claimed at all, e.g., rice power or laxative. A third contained unlisted substances.[19][20]

Only 0.3% of the 55,000 U.S. market dietary supplements were studied so that their common side effects are known.[18]

Society and culture

Use as food replacement

In early 20th century there were great hopes for supplements, but later research has shown these hopes were unfounded.[24]

"Antioxidant paradox" means the fact that even though fruits and vegetables are related to decreases in mortality, cardiovascular diseases and cancers, antioxidant nutrients do not really seem to help. According to one theory, this is because some other nutrients would be the important ones.[25][26] Multivitamin pills have neither proved useful[4] but may even increase mortality.[27]

Omega-3 fatty acids and fish oils from food are very healthy, but fish oil supplements are recommended only for those suffering from coronary artery diseases and not eating fish. Latest research has made the benefits of the supplements questionable even for them. Contrary to claims, fish oils do not decrease cholesterol but may even raise the "bad" LDL cholesterol and cause other harms. Also the use of cod liver oil is criticized by scientists.[28]

Alice Lichtenstein, DSc, chairwoman of the American Heart Association (AHA) says that even though omega-3 fatty acids from foods are healthy, the same is not shown in studies on omega-3 supplements. Therefore one should not eat fish oil supplements unless one suffers from heart diseases.[29]

Substances which the FDA regulates as food are subdivided into various categories, including foods, food additives, added substances (man-made substances which are not intentionally introduced into food, but nevertheless end up in it), and dietary supplements. The specific standards which the FDA exercises differ from one category to the next. Furthermore, the FDA has been granted a variety of means by which it can address violations of the standards for a given category of substances.

Regulation in European Union

The European Union's Food Supplements Directive of 2002 requires that supplements be demonstrated to be safe, both in dosages and in purity.[30] Only those supplements that have been proven to be safe may be sold in the bloc without prescription. As a category of food, food supplements cannot be labeled with drug claims but can bear health claims and nutrition claims.[31]

The dietary supplements industry in the United Kingdom (UK), one of the 28 countries in the bloc, strongly opposed the Directive. In addition, a large number of consumers throughout Europe, including over one million in the UK, and various doctors and scientists, had signed petitions by 2005 against what are viewed by the petitioners as unjustified restrictions of consumer choice.[32]

Although the European Court of Justice's Advocate General subsequently said that the bloc's plan to tighten rules on the sale of vitamins and food supplements should be scrapped,[35] he was eventually overruled by the European Court, which decided that the measures in question were necessary and appropriate for the purpose of protecting public health. ANH, however, interpreted the ban as applying only to synthetically produced supplements—and not to vitamins and minerals normally found in or consumed as part of the diet.[36]

Nevertheless, the European judges acknowledged the Advocate General's concerns, stating that there must be clear procedures to allow substances to be added to the permitted list based on scientific evidence. They also said that any refusal to add the product to the list must be open to challenge in the courts.[37]

Research

Effects of most dietary supplements have not been determined in randomized clinical trials and manufacturing is lightly regulated; randomized clinical trials of certain vitamins and antioxidants have found increased mortality rates.[38][39]

Committee on the Framework for Evaluating the Safety of Dietary Supplements, Food and Nutrition Board, Board on Life Sciences, Institute of Medicine and National Research Council of the National Academies (2004). Dietary supplements a framework for evaluating safety. Washington, D.C.: National Academies Press. p. ES-1-ES-3. ISBN0-309-09206-X.

^Skip the Supplements, Paul A. Offit, chief of the division of infectious diseases at the Children’s Hospital of Philadelphia, and Sarah Erush, the clinical manager in the pharmacy department of the Children’s Hospital of Philadelphia. The New York Times, December 14, 2013.